The goal of this project is to understand how non-human animals come to treat physically different stimuli as behavioral equivalents in ways that cannot be explained by perceptual similarity. Using standard, two-choice conditional discriminations common to studies of other basic learning and memory processes, the project will assess the effectiveness of different training experiences in producing acquired stimulus equivalences and why some experiences are more effective than others despite considerable overlap. In the proposed studies, different discriminative stimuli will initially share a common relationship to another stimulus and/or response. Afterwards, equivalences between the different but commonly associated discriminative stimuli will be evaluated by directly training new responses to some of them and then observing whether or not the remaining stimuli also control the new responses. In short, will the new behavioral function generalize from the directly trained to the untrained (test) stimuli, as expected if the sets are equivalent? A major focus of this research is to assess whether or not conditioning of a common, mediating representation to the discriminative stimuli during training is the source of such generalization and what that mediating representation might be. The results will be important for understanding how novel behavior, one notable human characteristic, can also emerge in other animals despite the absence of direct (reinforced) training and any known language ability.